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#Post#: 1115--------------------------------------------------
Re: Problem of the week-29/10/12
DIR By: Jeffrey Chan
Date: November 13, 2012, 9:25 am
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Cu is anode and Fe is cathode. Metals can only undergo oxidation
in normal conditions. Oxidation occurs at anode. So Cu electrode
dec in mass.
#Post#: 1116--------------------------------------------------
Re: Problem of the week-29/10/12
DIR By: Jeffrey Chan
Date: November 13, 2012, 9:28 am
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Well but if Cu --> Cu(II) ions then the colour change would have
been to blue...
#Post#: 1117--------------------------------------------------
Re: Problem of the week-29/10/12
DIR By: Michel
Date: November 13, 2012, 1:00 pm
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Again, getting closer to the answer! But a few rough edges must
be smoothened;)
Hint: Yes, you're right, Oxidation occurs at the anode, but what
species are oxidized? How does this oxidation affect the other
components of the electrolytic cell?
#Post#: 1119--------------------------------------------------
Re: Problem of the week-29/10/12
DIR By: Michel
Date: November 13, 2012, 3:48 pm
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--- Quote from: Jeffrey Chan link ---
>
> Cu is anode and Fe is cathode. Metals can only undergo
oxidation in normal conditions. Oxidation occurs at anode. So Cu
electrode dec in mass.
>
--- End Quote ---
Correct, Cu electrode will decrease in mass,
remember also that a potential of 12V across both electrodes
mean that reactions that are normally non spontaneous become
spontaneous, and also rapid.
#Post#: 1120--------------------------------------------------
Re: Problem of the week-29/10/12
DIR By: Jeffrey Chan
Date: November 13, 2012, 4:49 pm
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Chloride oxid to Cl2. Cl2 attack Cu to form CuCl2
#Post#: 1121--------------------------------------------------
Re: Problem of the week-29/10/12
DIR By: Michel
Date: November 13, 2012, 11:44 pm
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Correct, now something important happens after this...remember
Cu2+ is a new ion in solution...
#Post#: 1122--------------------------------------------------
Re: Problem of the week-29/10/12
DIR By: Jeffrey Chan
Date: November 14, 2012, 1:31 am
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Copper(II) ions react with the iron electrode to form iron(II)
ions (or iron(III)???)
#Post#: 1124--------------------------------------------------
Re: Problem of the week-29/10/12
DIR By: Michel
Date: November 14, 2012, 12:29 pm
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And that's the answer!
Thumbs up Jeffrey
The Fe + Cu2+ ==> Fe2+ + Cu results in the displacement of Cu2+
by Fe2+ and depositing Cu on the Fe electrode surface, this
means the mass change in the Fe electrode isn't much, although
there's a significant mass change. This reaction is so fast that
the color of the solution is green. The green Fe2+ is then
oxidized by atmospheric oxygen to Fe3+ subsequently.
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